What does "...Type" signify in Go function parameters?

Unveiling the Meaning of "...Type" in Go

In Go, the "..." syntax appears in the parameter list of a function to indicate that the final parameter is variadic. Variadic functions can accept any number of arguments for that parameter.

Referring to the append function in builtin.go:

func append(slice []Type, elems ...Type) []Type

The "...Type" denotes that the elems parameter is variadic, which means it can receive multiple arguments of type Type. The code serves as documentation but is not compiled.

The following example demonstrates the usage of variadic parameters:

<code class="go">package main

import "fmt"

func main() {
   s := []int{1,2,3,4,5}
   s1 := s[:2]
   s2 := s[2:]
   s3 := append(s1, s2...)
   fmt.Println(s1, s2, s3)
}</code>

Output:

[1 2] [3 4 5] [1 2 3 4 5]

In this example, the append function accepts two arguments: the slice s1 and the variadic argument s2. The "...s2" syntax allows us to pass all elements of s2 as individual arguments to append. This effectively concatenates s1 and s2 into a new slice s3.

The "..." syntax provides flexibility when calling variadic functions, making them suitable for situations where the number of arguments is not fixed.

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